1. Field of Invention
The present invention relates to a time adjustment device that adjusts the time based on time information contained in signals transmitted from the base station of a CDMA (Code Division Multiplex Access) cell phone network, for example. The invention also relates to a timepiece having the time adjustment device, and to a time adjustment method.
2. Description of Related Art
Time information is contained in signals transmitted to cell phones from the base stations in modern CDMA cell phone networks. This time information is extremely precise time information that matches the GPS time, which is based on the atomic clocks on GPS (Global Positioning System) satellites.
Japanese Unexamined Patent Appl. Pub. JP-A-2000-321383 (see the abstract) teaches a terminal that acquires the GPS time data transmitted from a base station of a CDMA cell phone network, and uses the GPS time data to correct the time kept by an internal clock.
In order for the time adjustment device to receive the time data transmitted from the base station of a CDMA cell phone network, a specific Walsh code, for example, must be mixed with the signal transmitted from the base station. The time adjustment device must therefore have an internal Walsh code generator.
There are, for example, 64 different Walsh codes. The scale of the device circuits for generating these Walsh codes is necessarily large, which also creates the problem of increased power consumption.